turboguard

As title says, if I adjust my mixture screws and idle air bleed valve to get the proper 30 degree dwell, my car idles like crap...vacuum drops about an inch every second and sounds like its missing. However, if I adjust the mixture to make it more rich, the idle evens out wonderfully and holds at 21 inches of vacuum, but the dwell meter is pegged at 54!

I also just installed a brand new AC Delco O2 sensor and the Bosch one that was in there was pretty blackened, although it was also only a few months old. The new sensor didn't seem to make a difference in the readings.

What in the world is going on here?

Forgot to mention that all of the emissions devices have been removed except for the EGR (smog/air pump/tubing, evap canister, and cat) but the engine otherwise is stock.

backtothe80s

When you made the adjustments, were they done per the FSM? Vacuum/exhaust leaks? Any play in the throttle shaft bushings?

turboguard

It's a "brand new" throttle plate from Cliff's I got to clear up the last of my vacuum leak issues. I might still have a slight exhaust leak where the manifolds connect to the Y-pipe (I tried to patch it up best I can until I can afford headers), but wouldn't that cause the O2 sensor to read slightly lean instead of rich anyway?

Also the engine decided to throw a couple of codes today when I got home from work and was just idling in the car...the idle sounded high for some reason then suddenly it dropped down to normal and threw codes 13 and 45. This is getting very irritating...

backtothe80s

Yes, it would cause it to be lean. It could be adding to your driveability issues. I'm not sure. Diagnose the code 13 before doing anything else. I had that on my `89 and it turned out the wire going from the ECM to ground for the O2 sensor circuit was open. Easy fix.

It's very important to prep the car per the FSM before making adjustments to the E-Qjets. I'm not sure about your car, but on some, you have to block certain vacuum lines coming from the evap canister before adjusting mixture.

I feel your pain! Keep at it!

JA411

You need actual 02 and MC readings. If the exhaust leak is making 02 lean in closed loop ECM is going to enrich mixture. At extended idle most single wire 02's go back to open loop. There are standard adjustment setting tools for electronic controlled carb. That is good reference points. Basic float level adjustment is also critical. Leaking well plugs are common, make sure to seal properly. To many other factors and adjustments are critical as well.
Joe

turboguard

I just decided to ditch the multimeter and timing light and do everything by ear/feel.
I decided to leave the ECM plugged in to the distributor since whenever I set to the proper number and hooked it back up, it ran pretty bad.

So I whipped out my vacuum gauge and first set the timing to maximum steady vacuum.

Then I further tweaked the carb air bleed and mixture screws for maximum vacuum with minimal missing/steady needle. I ended up turning the idle air bleed valve all the way in and the idle mixture screws 5 turns out each to give me the best vacuum pull and smoothest idle.

I could already tell it was way better driving to work today, I didn't have any of the hard shaking at idle or the chuggles I normally got at part throttle.

I'm guessing just the age of the engine and all the electronics just make them unreliable to tune by in these cars?

five7kid

iTrader: (14)

I wouldn't say that. My '82 Berlinetta LG4 with 304k miles on it tuned up and ran great when everything was set to factory specs (admittedly back in 2007). It did have a fully rebuilt carb on it, new EGR valve, replacement cat and was otherwise well maintained. But that's a lot of miles regardless of age (the engine had never been opened up). And it passed the roller sniffer emissions test here with flying colors (after failing before I set everything to factory).

Codes 13 and 45 indicate a problem with the O2 sensor. Figure that out. It may run fine in open loop without the O2 sensor working, but it won't when it warms up and goes into closed loop.

naf

iTrader: (7)

the ccc system will idle better with the settings on the rich side and in non-feedback mode. under normal open loop the ecm will be constantly hunting the 'ideal' mixture setting and you will see some variance in idle quality. You'll see this with the dwell meter swinging back and forth slightly around 30 degrees when properly set. your idle shouldn't be crazy but a slight variance of idle quality is normal, like barely noticeable from the cabin at a light maybe.

IOTW your rich settings are keeping it in open loop and your smooth, steady idle is likely masking the real problem.

Trashman88

I'm trying to set the mixture on my 85 Iroc using the dwell spec also but I'm unsure of how to hook up the meter and I can't seem to find any DETAILED info on how to connect it properly.

turboguard

Any clues as to what the real problem could possibly be? When set to factory it definitely has a noticeable "shudder" every second or so and sometimes surges at part throttle. The O2 sensor is a brand new AC Delco one. Carb has been rebuilt using Cliff parts with brand new sensors. Distributor is a brand new Spectra Premium unit from rockauto. Plugs and wires are new. Fuel pump is new "carter-style" from Orielly's. Doesn't seem to be burning oil, I don't get any smoke out of my tailpipes even on cold startups. The only thing I have yet to do is a compression test on the cylinders.

The only other thing that is giving me trouble is that it is overheating...especially with the A/C on. I have to turn the A/C off during my 30 minute drive home on hot days or it will actually read past the last line on the guage.

naf

iTrader: (7)

computer controlled dist? timing set to 0-4 degrees advanced with the esc unplugged and verified to be around 22ish at idle with the esc plugged back in?

verify all ignition components are working properly and timing is good before dickering with the carb.

next confirm that the TPS is set correctly to read near 0.40V at idle and near 4.0V at WOT.

A scanner that reads and displays 'real' time is helpful for troubleshooting.

the higher than expected run temps are likely the result of an out of tune motor.

turboguard

Yep I've been doing things by the book (literally, I have the FSM) to no avail. I even have the Thexton tools for the carb as well.

Would bad valve parts cause any of my issues?

naf

iTrader: (7)

which valve parts?

turboguard

Like worn valve guides, seals, springs, etc...

I would love to tear the heads off just to check the cylinders and do a valve job but its hard since this is my daily driver lol

turboguard

So a little update...It was extra hot today and the car was getting pretty warm as well, and I was sitting at a stop the engine began to struggle and eventually just softly died.

So...ignition issue? Bad coil or icm? Even though they are both new with the dizzy?

Luckily it started back up...it struggled for a minute to put out any power but eventually got up to speed.

I still don't know why it would be overheating so drastically even with the AC off...The coolant is fresh and I've been trying to burp it like every day. Coolant isn't going down either.

Another note, when its hot out it has a slight ping if I floor it in high gear (I assume that rattling can noise from the engine is a knock)...but I have a relatively new knock sensor! Is my wiring harness/computer just FUBAR or what?

This is all getting really discouraging, I've put so much time and money into it already...

naf

iTrader: (7)

try setting your timing back. try about 5 degrees less at a time and see how it does, WITH the dwell meter hooked up. you may have to re-adjust the dwell with the new timing setting.

don't worry about the heads, if something there is bad enough to cause problems, you'd know it

turboguard

Would a bad battery or alternator possibly damage an ignition coil or module?

Trashman88

I can't say for sure. But I have never ran into that myself and I have never heard of that happening to anyone.

turboguard

Alright, I bought a new module from summit but I'm still waiting for my new Tuff Stuff 140 amp alternator to come in, but I was itching to pop the new module in to see if there was any difference in how it acted.

RocketyMan

I'm trying to follow all the posts here. @turboguard, where are you at on this? Did you confirm yet whether or not you are getting closed loop? You said your dwell was pegged out...is this still happening?

As far as dwell...are you connecting up one lead to GND and one lead to the green connector next to the blower motor???

Me personally, I don't like those old-skool dwell meters as they are fragile and fidgety. I use a multi meter DMM with dwell.





See the selection that shows "HZ %" This is where I select my meter and use the mode selection for percent. The Hz will be 30 Hz as this is a PWM signal. So move your DMM to % to show the dwell time. You want to have a hot engine WITH air cleaner installed showing around 50% dwell. This is best so that your ECM can adjust either way.

I hope that makes sense.


*edit* .... lol.

FYI, the L69 runs very rough UNTIL it gets into closed loop. It's just the nature of the beast. If you're still unsure about anything, I can post a picture from one of my set-ups.

turboguard

Yeah I actually use a nice Bosch multimeter with a dedicated dwell setting. I popped in a new ICM and ignition coil and it seems to run a lot better now, and I can actually get it within the proper dwell range without it idling like crap.

But I have a new problem now...it's overheating, and running lean I believe. I still get the occasional bucking at part throttle, and sometimes when I'm cruising and I punch it to pass it bogs down and backfires out of the carb.

As far as the overheating, I've made sure the area between the A/C core and the cooling core was cleared of debris, I bought a brand new severe duty fan clutch, a high performance 180 degree thermostat, and I did a coolant flush with the prestone stuff (although the coolant that was already in there looked pretty good as it was coming out). I drained the engine block too where the knock sensor screws onto, and filled it up with 50/50 prestone and made sure to bleed it the best I could. Even with the A/C off, during hot days it gets right to the red, and goes over it if I have the A/C on.

I also thing the trans is overheating too because once it gets really hot and I punch it, it feels like it starts slipping from 2-3. I have the timing set just a bit above 0, although if I plug everything back in and twist the distributor, I have very little wiggle room in either direction before it starts idling very rough.

I'm kind of at a loss right now. I really need a new engine lol

naf

iTrader: (7)

the engine is probably fine.

when you set timing and reconnect the four wire connector does the timing read around 20ish degrees?

RocketyMan

naf is right about the timing and most likely your engine is fine as well. It just needs to be set right. Seems to coincide with your backfiring through carburetor...

An engine with not enough timing will "overheat" because it has to work harder. This could be a partial cause to your issue.

But as far as setting the dwell, that should be last after initial base timing is set and any other adjustments. And again, unless the car is in closed loop, it'll "run like crap" until it does so. If i'm not mistaken, there is a timer for how long you can remain in open loop before a code is set.

turboguard

So I whipped out my timing light and unplugged my ECM and set the timing to what was supposedly 8 BTDC (I don't know how accurate my timing marks are) and jumps up to 30 with the ECM plugged in. I did notice that it started easier and seemed to run better (more responsive?) today, but it still got close to red without A/C, and up to the red with A/C.

I guess my temp gauge could be wildly inaccurate...but it still makes me nervous, especially with the transmission acting up when it gets hot.

RocketyMan

If you have a paint pen, it REALLY helps marking the balancer mark.

As far as the temperature issue, do you have one of the infared guns? I'd point it at your Tstat when the gauge is at around 220F or whichever to see how accurate the temp gauge actually is. I'd be curious to know if your temp sender is bad.

turboguard

Another thing I found odd was that after I drained my coolant through the radiator and the engine block, it took less than what I thought it would to fill it back up. According to my service manual it takes 4.3 gallons of coolant, so I purchased 5 gallons of some premixed. After filling up the radiator, turning the engine on and filling it up again as far as it would go and filling up the reservoir, I had almost 2 gallons of coolant left over!

I also have one of those prestone flush kit T fittings on my upper heater core hose and left it open as I filled the system to aid with letting the air out. After the system warms up the upper radiator hose definitely gets tight and hot so I know everything is pressurizing and flowing good, and my heat works great in the car. I also made sure to open the pressure release on my radiator cap to where it fills up the reservoir and then shake the whole car and squeeze the tubes to burp any leftover air out after a drive (it then pulls the coolant back out of the reservoir as it cools down appropriately).

So there's another mystery...